As disclosed in, for example, Patent Document I (see below), humidity control systems, for regulating the level of humidity in the air by the use of an adsorbent and by performing a refrigeration cycle, are well known in the conventional technology. Such a humidity control system is provided with two adsorption units. Each adsorption unit is made up of an adsorbent-filled mesh container and a refrigerant line which is passed completely through the mesh container. The refrigerant line of each adsorption unit is fluidly connected to a refrigerant circuit which performs a refrigeration cycle. In addition, the humidity control system is provided with dampers for effecting switching of the air which is delivered to each adsorption unit.
During the operation of the above-described humidity control system, the compressor of the refrigerant circuit operates and a refrigeration cycle is performed in which one of the two adsorption units becomes an evaporator while the other adsorption unit becomes a condenser. In addition, the direction in which the refrigerant is circulated in the refrigerant circuit is changed by controlling a four-way valve, whereby each adsorption unit alternately functions as an evaporator and as a condenser.
When the humidity control system is in a humidification mode of operation, supply air flowing from the outside to the inside of the room is directed to one adsorption unit which becomes a condenser. The supply air is humidified with moisture desorbed from the adsorbent. At that time, exhaust air flowing from the inside to the outside of the room is directed to the other adsorption unit which becomes an evaporator and the adsorbent recovers moisture present in the exhaust air. On the other hand, when the humidity control system is in a dehumidification mode of operation, supply air flowing from the outside to the inside of the room is directed to one adsorption unit which becomes an evaporator and the adsorbent adsorbs moisture present in the supply air. At that time, exhaust air flowing from the inside to the outside of the room is directed to the other adsorption unit which becomes a condenser. Moisture desorbed from the adsorbent is discharged together with the exhaust air to outside the room.
In addition, as a means capable of functioning in the same way as the aforesaid adsorption units, a heat exchange member, as disclosed in, for example, Patent Document II (see below), has been known in the conventional technology. In this heat exchange member, plate-shaped fins are arranged around a copper pipe and adsorbent is supported on the surface of the copper pipe and on the surface of each fin. And the heat exchange member is configured such that the adsorbent is heated and cooled with fluid flowing through the copper pipe.
Additionally, as a humidity control system of the above-described type, there is proposed a humidity control system as shown in Patent Document III (see below). In this humidity control system, an air passageway for providing fluid communication between an outdoor space and an indoor space is formed in the casing and an adsorption element is disposed in the air passageway. Outdoor air (OA) is distributed through the adsorption element so that it adsorbs thereon moisture present in the outdoor air (OA). Then, the outdoor air (OA) is supplied, as dehumidified air (humidity controlled air (SA)), to the indoor space. In addition, it is arranged such that, for example, moisture adsorbed on the adsorption element is desorbed; the desorbed moisture is fed to outdoor air (OA); and the outdoor air (OA) is supplied, as humidified air (humidity controlled air (SA)) to the indoor space.    Patent Document I: JP H8-189667A    Patent Document II: JP H7-265649A    Patent Document III: JP H9-329371A